-echo #display textenv #display the env varexport #set shell var to env varpwd #display working directoryset #show all the var and its valueunset #remove the var unset iexec #after exec then give the exec control ?cut #cut input txt $cut -d ":" -f 1,3 /etc/groupcat #read the STDINP then redirect to the STD outputtac #the same of cat but first in last outhead #print the head part $head -5 myfiletail #print the tail part expand # expand the tab to spaceunexpand #change the space to tabfmt #format the file $fmt -w 100 fileA > fileBjoin #join the same part of filespaste #combline the lines of filesnl #insert the number of line od #view the binary file 歐弟strings #view the strings in the binary filepr #format the file to printsplit # split file !!! no e